Ice Crystal Number Research Articles

A Process Study on Thinning of Arctic Winter Cirrus Clouds With High‐Resolution ICON‐ART Simulations

AbstractIn this study, cloud‐resolving simulations of a case study for a limited area of the hibernal Arctic were performed with the atmospheric modeling system ICON‐ART (ICOsahedral Nonhydrostatic‐Aerosol and Reactive Trace gases). A thorough comparison with data both from satellite as well as aircraft measurement is presented to validate the simulations. In addition, the model is applied to clarify the microphysical processes occurring when introducing artificial aerosol particles into the upper troposphere with the aim of modifying cirrus clouds in the framework of climate engineering. Former modeling studies investigating the climate effect of this method were performed with simplifying assumptions and much coarser resolution, reaching partly contradicting conclusions concerning the method's effectiveness. The primary effect of seeding is found to be a reduction of ice crystal number concentrations in cirrus clouds, leading to increased outgoing longwave radiative fluxes at the top of the atmosphere, thereby creating a cooling effect. Furthermore, a secondary effect is found, as ice crystals formed from the injected seeding aerosol particles lead to enhanced riming of cloud droplets within the planetary boundary layer. This effectively reduces the coverage of mixed‐phase clouds, thus generating additional cooling by increased upward longwave radiative fluxes at the surface. The efficacy of seeding cirrus clouds proves to be relatively independent from the atmospheric background conditions, scales with the number concentrations of seeding particles, and is highest for large aerosol particles.

The Impact of Mesoscale Gravity Waves on Homogeneous Ice Nucleation in Cirrus Clouds

AbstractEffects of a spectrum of mesoscale gravity waves on homogeneous aerosol freezing in midlatitude cirrus are studied by means of parcel model simulations that are driven by random vertical wind speeds constrained by balloon measurements. Stochastic wave forcing with mean updraft speeds of 5–20 cm/s leads to substantial nucleated ice crystal number concentrations (ICNC) of 0.1–1 cm−3 in situations with slow large‐scale cooling, which by itself would generate fewer ice crystals. The stochastic nature of wave‐driven air parcel temperatures enhances ICNC even further, but the times required to reach freezing conditions unsupported by large‐scale cooling may vary widely. In the presence of wave forcing, ice crystals with low ICNC (<1–10 L−1) are also generated by homogeneous freezing, albeit only rarely. Comparisons with aircraft measurements suggest significant influences of heterogeneous ice‐nucleating particles and ice crystal sedimentation on ICNC, but quantifying their individual contributions remains elusive.

Sensitivity of WRF model simulations to parametrizations of depositional growth of ice crystal during the landfall of Typhoon Fitow (2013)

AbstractUncertainty in the ice nucleation process is still large, yet the torrential precipitation associated with the landfall of a typhoon is strongly contributed by stratiform rainfall, mainly composed of ice‐phase clouds. This study investigates the ice growth parametrization proposed by Zeng et al. under the assumption that the ice crystal concentration is proportional to the mass of ice crystal. Sensitivity tests reveal that simulations with the Zeng scheme are especially sensitive to ice nuclei concentration. Zeng schemes with high ice crystal concentration simulate anomalously large rain rate, weak intensities and abnormal tracks, and this is directly related to the over‐production of ice nuclei concentration propagating into cloud ice and other microphysical fields mainly through the depositional growth of cloud ice from cloud water (PIDW). The Shen et al. scheme works better than the Zeng scheme by changing the radius of base ice crystal from 0 to 40 µm and reducing sensitivity of PIDW to the ice nuclei concentration. But Shen schemes simulate the number of ice crystals as anomalously large as those in Zeng schemes, since both Zeng and Shen schemes use the Fletcher equation in the parametrization of ice crystal concentration. When DeMott et al. ice crystal concentration parametrization is applied to the Zeng scheme, the anomalously large rainfall is significantly weakened, further indicating that Zeng schemes with high ice crystal concentration poorly simulate a typhoon, primarily due to the over‐nucleation of ice in the Fletcher parametrization.

Variability in Contrail Ice Nucleation and Its Dependence on Soot Number Emissions

AbstractContrail ice nucleation is mainly controlled by aircraft emissions and the atmospheric state. The nucleation rate can have a strong impact on microphysical processes, optical properties, lifetime, and, therefore, on the climate impact of contrail cirrus. We study contrail ice crystal formation offline for specified atmospheric conditions and its spatial variability in a global climate model. Assuming the standard atmosphere, above around 270 hPa (10 km) contrail ice nucleation is mainly controlled by aircraft soot number emissions and below additionally by atmospheric temperature. Parameterizing contrail ice nucleation in a global climate model, we find that in the northern extratropics contrails form frequently far away from their formation threshold. For current soot number emissions and in case of contrail formation, 90% of emitted soot particles form on average ice crystals around the cruise level and more than 70% between cruise altitudes and 300 hPa. The number of nucleated ice crystals in the extratropics decreases nearly at the same rate as soot number emissions. In contrast, in the tropics around cruise altitudes approximately 60% of contrails develop close to their formation threshold so that on average only about 50% of emitted soot particles can form ice crystals. Below, contrail formation occurs rarely and ice nucleation is reduced more strongly. Of the main air traffic areas, contrail ice nucleation is significantly limited by the atmospheric state over eastern Asia and over the southeastern United States. This limitation is enhanced during the summer months.

New type of evidence for secondary ice formation at around −15 °C in mixed-phase clouds

Abstract. Ice crystal numbers can exceed the numbers of ice-nucleating particles (INPs) observed in mixed-phase clouds (MPCs) by several orders of magnitude, also at temperatures that are colder than −8 ∘C. This disparity provides circumstantial evidence of secondary ice formation, also other than via the Hallett–Mossop process. In a new approach, we made use of the fact that planar, branched ice crystals (e.g. dendrites) grow within a relatively narrow temperature range (i.e. −12 to −17 ∘C) and can be analysed individually for INPs using a field-deployable drop-freezing assay. The novelty of our approach lies in comparing the growth temperature encoded in the habit of an individual crystal with the activation temperature of the most efficient INP contained within the same crystal to tell whether it may be the result of primary ice formation. In February and March 2018, we analysed a total of 190 dendritic crystals (∼3 mm median size) deposited within MPCs at the high-altitude research station Jungfraujoch (3580 m a.s.l.). Overall, one in eight of the analysed crystals contained an INP active at −17 ∘C or warmer, while the remaining seven most likely resulted from secondary ice formation within the clouds. The ice multiplication factor we observed was small (8), but relatively stable throughout the course of documentation. These measurements show that secondary ice can be observed at temperatures around −15 ∘C and thus advance our understanding of the extent of secondary ice formation in MPCs, even where the multiplication factor is smaller than 10.

Homogeneous nucleation from an asymptotic point of view

The major formation pathway of ice crystals in the low-temperature regime below $${235}\hbox { K}$$ is homogeneous freezing of solution droplets. This mechanism is known to be very sensitive to environmental conditions, i.e., temperature and humidity. Nucleation events are characterized by an explosive increase in ice crystal number concentrations. For a better understanding of ice nucleation in this temperature regime, we have to analyze these nucleation events carefully. In this study, we consider the description of a single nucleation event using a slightly simpler system which features the same sharp increase in ice crystal number concentration. We analyze the simpler system with the help of asymptotic methods and construct a leading order approximation to the exact solution. This gives insight into a single homogeneous nucleation event from a mathematical perspective, without introducing further assumptions apart from the transition to the simplified system. In addition, we use the asymptotic approximation to construct a new parameterization, relating the updraft velocity to the homogeneously nucleated number of ice crystals, and compare the results with a widely used parameterization.

Lidar/radar approach to quantify the dust impact on ice nucleation in mid and high level clouds

We present the first attempt of a closure experiment regarding the relationship between ice nucleating particle concentration (INPC) and ice crystal number concentration (ICNC), solely based on active remote sensing. The approach combines aerosol and cloud observations with polarization lidar, Doppler lidar, and cloud radar. Several field campaigns were conducted on the island of Cyprus in the Eastern Mediterranean from 2015-2018 to study heterogeneous ice formation in altocumulus and cirrus layers embedded in Saharan dust. A case study observed on 10 April 2017 is discussed in this contribution.

Contrail Formation: Analysis of Sublimation Mechanisms

AbstractWe study losses of ice crystals in a persistent, soot‐rich contrail in the wake behind a medium‐sized aircraft at cruise. Constraining a model covering ice nucleation, growth, and sublimation phases with an aircraft data set, we track the sublimation history over 2 min of contrail age and relate ice crystal numbers to the number of soot particles emitted by the aircraft engines. We analyze the observed vertical distribution of ice numbers, estimating an exponential scale height in the range 50–100 m and wake‐averaged ice numbers (1.3–1.7) × 1015 (kg‐fuel)−1 after sublimation, removing 60% of the ice crystals that originally nucleated on emitted soot particles. We define soot emission‐ and ice supersaturation‐dependent contrail depths, affecting estimates of horizontal spreading rates of contrails. Our findings have ramifications for the representation of long‐lived contrails in global models.

A Study of Enhanced Heterogeneous Ice Nucleation in Simulated Deep Convective Clouds Observed During DC3

AbstractThe impacts of enhanced heterogeneous ice nucleation (HET) on the properties of deep convective clouds (DCCs) have been investigated in cloud‐resolving simulations with the WRF‐CHEM model. The study focuses on a case observed during the Deep Convective Clouds and Chemistry (DC3) field campaign. For the simulated DCCs, which had cold cloud‐base temperatures, an inverse relationship exists between ice crystal mass produced through HET and anvil ice crystal number concentrations. This seems to be due to the indirect competition between HET and subsequent homogeneous freezing (HOM) for liquid droplets. Furthermore, our simulations suggest that HET enhancements at warmer temperatures are more efficient in depleting liquid droplets below and hence have larger impacts on anvil properties than HET enhancements at colder temperatures do. This temperature dependence indicates that similar increases in the number of ice nucleating particles (INPs) may potentially have different impacts on DCCs, depending on the INP type and at which temperatures they can nucleate ice crystals. We also found that the reduced anvil ice number concentrations due to the enhanced HET may lead to optically thinner anvil clouds. The reduction in cloud optical depth comes from a decrease in ice crystal mass concentrations, and in some runs also from an increase in ice crystal sizes. These results suggest potentially large impacts of INPs on the properties of DCCs, especially if precipitation is predominantly produced through ice processes in the DCCs. The results underscore the importance of fully understanding the temperature‐dependent ability of aerosol particles to nucleate ice crystals.

The effect of secondary ice production parameterization on the simulation of a cold frontal rainband

Abstract. Secondary ice production via processes like rime splintering, frozen droplet shattering, and breakup upon ice hydrometeor collision have been proposed to explain discrepancies between in-cloud ice crystal and ice-nucleating particle numbers. To understand the impact of this additional ice crystal generation on surface precipitation, we present one of the first studies to implement frozen droplet shattering and ice–ice collisional breakup parameterizations in a mesoscale model. We simulate a cold frontal rainband from the Aerosol Properties, PRocesses, And InfluenceS on the Earth's Climate campaign and investigate the impact of the new parameterizations on the simulated ice crystal number concentrations (ICNC) and precipitation. Near the convective regions of the rainband, contributions to ICNC can be as large from secondary production as from primary nucleation, but ICNCs greater than 50 L−1 remain underestimated by the model. The addition of the secondary production parameterizations also clearly intensifies the differences in both accumulated precipitation and precipitation rate between the convective towers and non-convective gap regions. We suggest, then, that secondary ice production parameterizations be included in large-scale models on the basis of large hydrometeor concentration and convective activity criteria.

Effect of dynamic storage temperatures on the microstructure of frozen carrot imaged using X-ray micro-CT

Frozen vegetables are often exposed to dynamic temperature conditions during cold storage and distribution chain. The resulting ice recrystallization leads to microstructural changes, which is directly linked to the final vegetable quality. To this end, X-ray μCT was applied to visualize and quantify 3D ice crystal changes in carrot over a period of two months of frozen storage with dynamically changing temperature. The studied conditions revealed a significant increase in ice crystal size during the storage period. The mean equivalent diameter of the ice crystals increased from 246 ± 15.9 μm, to 342 ± 13.2 μm, 394 ± 18.5 μm, 525 ± 28.0 μm and 578 ± 27.6 μm at 0 d, 7 d, 14 d, 30 d and 60 d of storage, respectively, while the number of ice crystals decreased. The 3D data on the ice crystals and image analysis presented within this paper provide an insight making it possible to describe microstructure evolution, and for better control cold storage sector of frozen vegetables.

Non-Monotonic Dependencies of Cloud Microphysics and Precipitation on Aerosol Loading in Deep Convective Clouds: A Case Study Using the WRF Model with Bin Microphysics

Aerosol-cloud-precipitation interactions in deep convective clouds are investigated through numerical simulations of a heavy precipitation event over South Korea on 15–16 July 2017. The Weather Research and Forecasting model with a bin microphysics scheme is used, and various aerosol number concentrations in the range N0 = 50–12,800 cm−3 are considered. Precipitation amount changes non-monotonically with increasing aerosol loading, with a maximum near a moderate aerosol loading (N0 = 800 cm−3). Up to this optimal value, an increase in aerosol number concentration results in a greater quantity of small droplets formed by nucleation, increasing the number of ice crystals. Ice crystals grow into snow particles through deposition and riming, leading to enhanced melting and precipitation. Beyond the optimal value, a greater aerosol loading enhances generation of ice crystals while the overall growth of ice hydrometeors through deposition stagnates. Subsequently, the riming rate decreases because of the smaller size of snow particles and supercooled drops, leading to a decrease in ice melting and a slight suppression of precipitation. As aerosol loading increases, cold pool and low-level convergence strengthen monotonically, but cloud development is more strongly affected by latent heating and convection within the system that is non-monotonically reinforced.

Mitigating the contrail cirrus climate impact by reducing aircraft soot number emissions

Contrail cirrus are a major component of the climate forcing due to air traffic. For a given contrail cirrus cover, ice water content and ice crystal shape, their impact on radiation is dependent on the number and size of ice crystals. Here we use a global climate model to study the impact of a reduction in initially formed ice crystal numbers, as may be caused by reduced soot number emissions. We find that for reduced initial ice crystal numbers the ice water content is decreased and ice crystal sizes increased, leading to a reduction in contrail cirrus optical depth and doubling the fraction of contrail cirrus that cannot be detected by satellite remote sensing. Contrail cirrus lifetimes and coverage are strongly reduced leading to significant reductions in contrail cirrus radiative forcing. The global climate impact of contrail cirrus is nonlinearly dependent on the reduction in initial ice crystal numbers. A reduction in the initial ice crystal number of 80% leads to a decrease in contrail cirrus radiative forcing by 50%, whereas a twofold reduction leads to a decrease in radiative forcing by approximately 20%. Only a few contrail cirrus outbreaks explain a large percentage of the climate impact. The contrail cirrus climate impact can be effectively mitigated by reducing initial ice crystal concentrations in such outbreak situations. Our results are important for assessments dealing with mitigating the climate impact of aviation and discussions about the use of alternative fuels or lean combustion in aviation.

Ice crystal number concentration estimates from lidar–radar satellite remote sensing – Part 2: Controls on the ice crystal number concentration

Abstract. The ice crystal number concentration (Ni) is a key property of ice clouds, both radiatively and microphysically. Due to sparse in situ measurements of ice cloud properties, the controls on the Ni have remained difficult to determine. As more advanced treatments of ice clouds are included in global models, it is becoming increasingly necessary to develop strong observational constraints on the processes involved. This work uses the DARDAR-Nice Ni retrieval described in Part 1 to investigate the controls on the Ni at a global scale. The retrieved clouds are separated by type. The effects of temperature, proxies for in-cloud updraft and aerosol concentrations are investigated. Variations in the cloud top Ni (Ni(top)) consistent with both homogeneous and heterogeneous nucleation are observed along with differing relationships between aerosol and Ni(top) depending on the prevailing meteorological situation and aerosol type. Away from the cloud top, the Ni displays a different sensitivity to these controlling factors, providing a possible explanation for the low Ni sensitivity to temperature and ice nucleating particles (INP) observed in previous in situ studies. This satellite dataset provides a new way of investigating the response of cloud properties to meteorological and aerosol controls. The results presented in this work increase our confidence in the retrieved Ni and will form the basis for further study into the processes influencing ice and mixed phase clouds.

Ice crystal number concentration estimates from lidar–radar satellite remote sensing – Part 1: Method and evaluation

Abstract. The number concentration of cloud particles is a key quantity for understanding aerosol–cloud interactions and describing clouds in climate and numerical weather prediction models. In contrast with recent advances for liquid clouds, few observational constraints exist regarding the ice crystal number concentration (Ni). This study investigates how combined lidar–radar measurements can be used to provide satellite estimates of Ni, using a methodology that constrains moments of a parameterized particle size distribution (PSD). The operational liDAR–raDAR (DARDAR) product serves as an existing base for this method, which focuses on ice clouds with temperatures Tc<-30 ∘C. Theoretical considerations demonstrate the capability for accurate retrievals of Ni, apart from a possible bias in the concentration in small crystals when Tc≳−50 ∘C, due to the assumption of a monomodal PSD shape in the current method. This is verified via a comparison of satellite estimates to coincident in situ measurements, which additionally demonstrates the sufficient sensitivity of lidar–radar observations to Ni. Following these results, satellite estimates of Ni are evaluated in the context of a case study and a preliminary climatological analysis based on 10 years of global data. Despite a lack of other large-scale references, this evaluation shows a reasonable physical consistency in Ni spatial distribution patterns. Notably, increases in Ni are found towards cold temperatures and, more significantly, in the presence of strong updrafts, such as those related to convective or orographic uplifts. Further evaluation and improvement of this method are necessary, although these results already constitute a first encouraging step towards large-scale observational constraints for Ni. Part 2 of this series uses this new dataset to examine the controls on Ni.

Implementation of a comprehensive ice crystal formation parameterization for cirrus and mixed-phase clouds in the EMAC model (based on MESSy 2.53)

Abstract. A comprehensive ice nucleation parameterization has been implemented in the global chemistry-climate model EMAC to improve the representation of ice crystal number concentrations (ICNCs). The parameterization of Barahona and Nenes (2009, hereafter BN09) allows for the treatment of ice nucleation taking into account the competition for water vapour between homogeneous and heterogeneous nucleation in cirrus clouds. Furthermore, the influence of chemically heterogeneous, polydisperse aerosols is considered by applying one of the multiple ice nucleating particle parameterizations which are included in BN09 to compute the heterogeneously formed ice crystals. BN09 has been modified in order to consider the pre-existing ice crystal effect and implemented to operate both in the cirrus and in the mixed-phase regimes. Compared to the standard EMAC parameterizations, BN09 produces fewer ice crystals in the upper troposphere but higher ICNCs in the middle troposphere, especially in the Northern Hemisphere where ice nucleating mineral dust particles are relatively abundant. Overall, ICNCs agree well with the observations, especially in cold cirrus clouds (at temperatures below 205 K), although they are underestimated between 200 and 220 K. As BN09 takes into account processes which were previously neglected by the standard version of the model, it is recommended for future EMAC simulations.

Modulating Intracellular Ice Growth with Cell-Permeating Small-Molecule Ice Recrystallization Inhibitors.

Ice formation remains central to our understanding of the effects of low temperatures on the biological response of cells and tissues. The formation of ice inside of cells and the net increase in crystal size due to recrystallization during thawing is associated with a loss of cell viability during cryopreservation. Because small-molecule ice recrystallization inhibitors (IRIs) can control the growth of extracellular ice, we sought to investigate the ability of two aryl-glycoside-based IRIs to permeate into cells and control intracellular ice recrystallization. An interrupted graded freezing technique was used to evaluate the IRI permeation into human red blood cells (RBCs) and mitigate cell damage during freezing and thawing. The effect of IRIs on the intracellular growth of ice crystals in human umbilical vein endothelial cells (HUVECs) was visualized in real time under different thawing conditions using fluorescence cryomicroscopy. Adding an aryl glycoside to 15% glycerol significantly increased post-thaw RBC integrity by up to 55% during slow cooling compared with the 15%-glycerol-only control group. The characteristics of the cryobiological behavior of the RBCs subjected to the interrupted graded freezing suggest that the aryl-glycoside-based IRI is internalized into the RBCs. HUVECs treated with the IRIs were shown to retain a large number of small ice crystals during warming to high subzero temperatures and demonstrated a significant inhibition of intracellular ice recrystallization. Under slow thawing conditions, the aryl glycoside IRI p-bromophenyl-β-d-glucoside was shown to be most effective at inhibiting intracellular ice recrystallization. We demonstrate that IRIs are capable of internalizing into cells, altering the cryobiological response of cells to slow and rapid freezing and controlling intracellular ice recrystallization during freezing. We conclude that IRIs have tremendous potential as cryoprotectants for the preservation of cells and tissues at high subzero temperatures.

A model intercomparison of CCN-limited tenuous clouds in the high Arctic

Abstract. We perform a model intercomparison of summertime high Arctic (> 80∘ N) clouds observed during the 2008 Arctic Summer Cloud Ocean Study (ASCOS) campaign, when observed cloud condensation nuclei (CCN) concentrations fell below 1 cm−3. Previous analyses have suggested that at these low CCN concentrations the liquid water content (LWC) and radiative properties of the clouds are determined primarily by the CCN concentrations, conditions that have previously been referred to as the tenuous cloud regime. The intercomparison includes results from three large eddy simulation models (UCLALES-SALSA, COSMO-LES, and MIMICA) and three numerical weather prediction models (COSMO-NWP, WRF, and UM-CASIM). We test the sensitivities of the model results to different treatments of cloud droplet activation, including prescribed cloud droplet number concentrations (CDNCs) and diagnostic CCN activation based on either fixed aerosol concentrations or prognostic aerosol with in-cloud processing. There remains considerable diversity even in experiments with prescribed CDNCs and prescribed ice crystal number concentrations (ICNC). The sensitivity of mixed-phase Arctic cloud properties to changes in CDNC depends on the representation of the cloud droplet size distribution within each model, which impacts autoconversion rates. Our results therefore suggest that properly estimating aerosol–cloud interactions requires an appropriate treatment of the cloud droplet size distribution within models, as well as in situ observations of hydrometeor size distributions to constrain them. The results strongly support the hypothesis that the liquid water content of these clouds is CCN limited. For the observed meteorological conditions, the cloud generally did not collapse when the CCN concentration was held constant at the relatively high CCN concentrations measured during the cloudy period, but the cloud thins or collapses as the CCN concentration is reduced. The CCN concentration at which collapse occurs varies substantially between models. Only one model predicts complete dissipation of the cloud due to glaciation, and this occurs only for the largest prescribed ICNC tested in this study. Global and regional models with either prescribed CDNCs or prescribed aerosol concentrations would not reproduce these dissipation events. Additionally, future increases in Arctic aerosol concentrations would be expected to decrease the frequency of occurrence of such cloud dissipation events, with implications for the radiative balance at the surface. Our results also show that cooling of the sea-ice surface following cloud dissipation increases atmospheric stability near the surface, further suppressing cloud formation. Therefore, this suggests that linkages between aerosol and clouds, as well as linkages between clouds, surface temperatures, and atmospheric stability need to be considered for weather and climate predictions in this region.

Impact of surface and near-surface processes on ice crystal concentrations measured at mountain-top research stations

Abstract. In situ cloud observations at mountain-top research stations regularly measure ice crystal number concentrations (ICNCs) orders of magnitudes higher than expected from measurements of ice nucleating particle (INP) concentrations. Thus, several studies suggest that mountain-top in situ cloud microphysical measurements are influenced by surface processes, e.g., blowing snow, hoar frost or riming on snow-covered trees, rocks and the snow surface. This limits the relevance of such measurements for the study of microphysical properties and processes in free-floating clouds. This study assesses the impact of surface processes on in situ cloud observations at the Sonnblick Observatory in the Hohen Tauern region, Austria. Vertical profiles of ICNCs above a snow-covered surface were observed up to a height of 10 m. The ICNC decreases at least by a factor of 2 at 10 m if the ICNC at the surface is larger than 100 L−1. This decrease can be up to 1 order of magnitude during in-cloud conditions and reached its maximum of more than 2 orders of magnitudes when the station was not in cloud. For one case study, the ICNC for regular and irregular ice crystals showed a similar relative decrease with height. This suggests that either surface processes produce both irregular and regular ice crystals or other effects modify the ICNCs near the surface. Therefore, two near-surface processes are proposed to enrich ICNCs near the surface. Either sedimenting ice crystals are captured in a turbulent layer above the surface or the ICNC is enhanced in a convergence zone because the cloud is forced over a mountain. These two processes would also have an impact on ICNCs measured at mountain-top stations if the surrounding surface is not snow covered. Conclusively, this study strongly suggests that ICNCs measured at mountain-top stations are not representative of the properties of a cloud further away from the surface.

Natural deep eutectic systems as alternative nontoxic cryoprotective agents

Natural deep eutectic systems (NADES) are mostly composed of natural primary metabolites such as sugars, sugar alcohols, organic acids, amino acids and amines. These simple molecules have been identified in animals living in environments with extreme temperature amplitudes, being responsible for their survival at negative temperatures during winter. Herein, we report for the first time the use of NADES based on trehalose (Treh) and glycerol (Gly) in cryopreservation, as cryoprotective agents (CPA). The evaluation of the thermal behaviour of these eutectic systems, showed that NADES have a strong effect on the water crystallization/freezing and melting process, being able to reduce the number of ice crystals and hence ice crystal damage in cells, which is a crucial parameter for their survival, upon freezing. Using this NADES as CPA, it is possible to achieve similar or even better cellular performance when compared with the gold standard for cryopreservation dimethyl sulfoxide (DMSO). In this sense, this work relates the physical properties of the NADES with their biological performance in cryopreservation. Our comprehensive strategy results in the demonstration of NADES as a promising nontoxic green alternative to the conventional CPA's used in cryopreservation methods.